Conventionally, a medical basket is known as a medical device that is trans endoscopically inserted into a body lumen and grasps a foreign material (a collected material) such as a calculus generated in the body lumen such as a bile duct. The medical basket generally includes a manipulating wire that is retractably inserted into a sheath having a long tube shape, and a basket unit that is provided at a distal end of the manipulating wire. The basket unit is made of a plurality of wires. A tip is fastened through a swaging process or the like, and thereby front ends of the plurality of wires are bundled. Rear ends of the plurality of wires are bundled by a connecting member, and are connected to the manipulating wire via the connecting member. When the foreign material is collected by the medical basket, the foreign material is grasped by the plurality of wires of the basket unit, and is removed from the body. However, in the medical basket, for example when the collected material is extremely large, if the basket unit is pulled into the sheath with the foreign material grasped, the foreign material cannot be collected because of impaction. Furthermore, in this case, the foreign material may not be detached from the wires of the basket unit. In the medical basket, when the foreign material causes impaction in this way, to prevent a need to perform a laparotomy, a mechanism capable of releasing the foreign material from the wires of the basket unit is proposed.
For example, in Japanese Patent No. 4226327 discloses a medical device having a handle, a sheath that is provided to extend from the handle in a distal direction and has a lumen extending from a distal end to a proximal end, a traction member that is disposed in the lumen of the sheath in an axial direction, and a basket that is connected to a distal end of the traction member. The basket of the medical device includes a plurality of wires, and a tip joint that is disposed at a distal end of the basket. Ends of the plurality of wires are fixed to the tip joint. This tip joint is configured to be deformed by a force smaller than a force that is required to break down the traction member or at least one of the wires of the basket, and the ends of the plurality of wires are configured to be removed from the tip joint. Thereby, in this medical device, when the foreign material causes impaction, the tip joint is deformed and separated from the wires, and the bundling of the wires is released. Thereby, the foreign material can be released from the basket. However, in this case, after the ends of the wires are removed from the tip joint, the tip joint remains in the body of the patient, and thus there is a need to perform another treatment in order to recover the tip joint.
In contrast, in Japanese Unexamined Patent Application, First Publication No. 2013-219 discloses a medical basket type treatment device having a manipulating wire that is disposed in a tubular sheath, a basket unit that is connected to a distal portion of the manipulating wire, and a distal end tip which is provided at a distal portion of the basket unit and bundles distal portions of a plurality of basket wires constituting the basket unit. This distal end tip has a fragile part with weaker strength than other portions of the distal end tip. When a force greater than or equal to a predetermined force is applied to the manipulating wire, the distal end tip is configured to be divided at the fragile part without breaking the manipulating wire. In this medical basket type treatment device, when the basket wires grasp the foreign material and impaction occurs, the manipulating wire is pulled to a proximal side. Thereby, when a force greater than or equal to a predetermined force acts on the manipulating wire and the basket wires, the manipulating wire or the basket wires are not broken, the distal end tip is broken into two pieces at the fragile part, and the foreign material can be released from the basket wires. In the medical basket type treatment device, even when the distal end tip is broken into the two pieces, each of the divided distal end tips is connected to the basket wires, and thus the distal end tip can be prevented from remaining in the body of the patient.
In Japanese Unexamined Patent Application, First Publication No. H10-165406 discloses a wire loop type treatment tool for an endoscope in which a plurality of elastic wires, which are integrally bundled at front and rear end sides and form loops, are coupled to a front end of a manipulating wire. In this treatment tool, distal end portions of the plurality of elastic wires are not bundled by another member, and are mutually joined by joining means such as soldering, brazing, or welding, and thereby are integrally bundled. In this treatment tool, a length of a joint of the front ends of the elastic wires is made to be shorter than that of a joint of the rear end sides of the elastic wires and that of a joint of the front end of the manipulating wire, and thereby junction of the front portions of the elastic wires is configured to be necessarily broken when an excessive force is applied to the elastic wires. In this treatment tool, when the elastic wires grasp the foreign material and impaction occurs, the junction of the front portions of the elastic wires is broken, and the foreign material can be released from the elastic wires. In this treatment tool, since the front portions of the plurality of elastic wires are bundled without using a distal end tip, the distal end tip does not remain in the body of the patient.